Retailers in Northern Ireland sold alcohol to more than one in four teenage mystery shoppers last year without asking for proof of age - the worst in the UK.

Some 297 alcohol sale tests were performed in pubs, bars and late night venues, supermarkets, convenience stores and petrol stations in 2016. All the testers were young-looking 18 and 19-year-olds.

Age ID was requested in 72% of visits before alcohol was handed over - the lowest pass rate in the UK.

While pass rates rose slightly (up 2% from 70% in 2015), test numbers fell by 24% - down from 393 tests in 2015.

Supermarkets performed the best, passing 80% of tests in 2016, while managed licensed premises were the worst with a pass rate of just 47%. The details were disclosed by retail age check auditors Serve Legal.

Statistics show the PSNI seized alcohol from under-18s 1,161 times in the past two years. Under-18s were admitted to hospital on 655 occasions with alcohol-related conditions in the past five years.

Ed Heaver, director of Serve Legal, said: "Retailers and operators of licensed premises in Northern Ireland have been extremely slow to adopt age-check testing for underage sales, with testing levels dwarfed by the rest of the UK.

"In 10 years of working with retailers, we have found that those that introduce regular independent testing programmes see compliance levels improve dramatically which reduces the risk of alcohol, tobacco and other harmful products getting into the hands of children.

"Age-check testing should be an integral part of retail training and operational best practice, not a panic purchase after a sting by trading standards or the police."

Retailers showed improvements in tobacco sale age checks in 2016, passing 71% of tests compared to 60% the previous year.

Test numbers also rose by 31% in 2016.

Action on Smoking and Health (ASH) reports that two thirds of smokers start smoking before the age of 18.

Of those who try smoking, between one third and one half will become regular smokers.

In 50 retail tests in 2016, knives were sold to more than four in 10 (45%) of young mystery shoppers without age checks.

The PSNI reported that 789 offences involving a knife or sharp instrument were recorded by police in 2015/16.

Glyn Roberts from Retail NI, which represents independent retailers, said there was a responsibility to ensure staff were properly trained.

"It does show some progress, for example in relation to tobacco, with fewer retailers selling to underage customers," he said.

"It should serve as a wake-up call to retailers about the need to stay within the law and ensure staff are aware of the law and are adequately trained."